[LeetCode] 3. Longest Substring Without Repeating Characters_Medium tag: two pointers
2021-08-05 01:24 Johnson_强生仔仔 阅读(19) 评论(0) 编辑 收藏 举报Given a string s
, find the length of the longest substring without repeating characters.
Example 1:
Input: s = "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3.
Example 2:
Input: s = "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1.
Example 3:
Input: s = "pwwkew" Output: 3 Explanation: The answer is "wke", with the length of 3. Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
Example 4:
Input: s = "" Output: 0
Constraints:
0 <= s.length <= 5 * 104
s
consists of English letters, digits, symbols and spaces.
Ideas:
visited record the letters we see so far in the range[l, r], if s[r] not in visited, r += 1, else continue l += 1 until s[r] not in visited
Code:
class Solution: def lengthOfLongestSubstring(self, s: str) -> int: ans, l, r, visited = 0, 0, 0, set() while r < len(s): if s[r] not in visited: visited.add(s[r]) r += 1 else: while s[r] in visited: l_c = s[l] visited.remove(l_c) l += 1 ans = max(ans, r - l) return ans